How to do MySQL Join and use PHP to get values
I am trying to write a mysql query to fetch data in this format:
<table>
<caption>table title and/or explanatory text</caption>
<thead>
<tr>
<th>User ID</th>
<th>First Name</th>
<th>Last Name</th>
<th>Field Name 1</th>
<th>Field Name 2</th>
<th>Field Name 3</th>
<th>Field Name 4</th>
<th>Field Name 5</th>
</tr>
</thead>
<tbody>
<?php
while ($row = mysqli_fetch_array($query)) {
echo "<tr>
<td>" .$row{'user_id'}. "</td>
<td>" .$row{'first_name'}. "</td>
<td>" .$row{'last_name'}. "</td>
<td>" .$row{'field_name_1'}. "</td>
<td>" .$row{'field_name_2'}. "</td>
<td>" .$row{'field_name_3'}. "</td>
<td>" .$row{'field_name_4'}. "</td>
<td>" .$row{'field_name_5'}. "</td>
</tr>";
}
?>
</tbody>
</table>
The tables in the database are formatted as follows.
Table: user_data p>
user_id | first_name | last_name |
------------------------------------------------------
1 | Jeff | Smith |
------------------------------------------------------
2 | Bob | Smith |
------------------------------------------------------
3 | Steve | Smith |
------------------------------------------------------
4 | Mary | Smith |
------------------------------------------------------
5 | Anna | Smith |
------------------------------------------------------
Table: custom_fields
custom_field_id | name |
-------------------------------------
3 | field name |
-------------------------------------
5 | field name |
-------------------------------------
7 | field name |
-------------------------------------
9 | field name |
-------------------------------------
11 | field name |
-------------------------------------
Table: custom_field_data p>
user_id | custom_field_id | value |
------------------------------------------------------
1 | 3 | XXXX |
------------------------------------------------------
1 | 5 | BBBB |
------------------------------------------------------
1 | 7 | CCCC |
------------------------------------------------------
1 | 9 | ZZZZ |
------------------------------------------------------
1 | 11 | YYYY |
------------------------------------------------------
2 | 3 | XXXX |
------------------------------------------------------
2 | 5 | BBBB |
------------------------------------------------------
2 | 7 | CCCC |
------------------------------------------------------
2 | 9 | ZZZZ |
------------------------------------------------------
3 | 3 | XXXX |
------------------------------------------------------
3 | 5 | BBBB |
------------------------------------------------------
3 | 9 | ZZZZ |
------------------------------------------------------
3 | 11 | YYYY |
------------------------------------------------------
I am looking for the best solution to query the data and then print it to screen using PHP or AJAX. Is it possible? Would it be better to use json? And a sample request would be great.
FYI: Ultimately, all data to be retrieved must be filtered on the screen. Thanks for the help.
My desired output would be
user_id | first_name | last_name | custom_field_3 | custom_field_5 | custom_field_7 | custom_field_9 | custom_field_11 |
-------------------------------------------------------------------------------------------------------------------------------------------------------------
1 | Jeff | Smith | XXXX | BBBB | CCCC | ZZZZ | YYYY |
-------------------------------------------------------------------------------------------------------------------------------------------------------------
2 | Bob | Smith | XXXX | BBBB | CCCC | ZZZZ | YYYY |
-------------------------------------------------------------------------------------------------------------------------------------------------------------
3 | Steve | Smith | XXXX | BBBB | CCCC | ZZZZ | YYYY |
-------------------------------------------------------------------------------------------------------------------------------------------------------------
4 | Mary | Smith | XXXX | BBBB | CCCC | ZZZZ | YYYY |
-------------------------------------------------------------------------------------------------------------------------------------------------------------
5 | Anna | Smith | XXXX | BBBB | CCCC | ZZZZ | YYYY |
-------------------------------------------------------------------------------------------------------------------------------------------------------------
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You can use the function group_concat
, https://dev.mysql.com/doc/refman/5.0/en/group-by-functions.html#function_group-concat , with my previous request to get one record per user ...
If you had a SQLfiddle I could test this, but like not, I have no data to test with ...
select ud.firstname, ud.lastname, group_concat(cf.name)
from user_data as ud
join custom_field_data as cfd
on cfd.user_id = ud.user_id
join custom_fields as cf
on cf.custom_field_id = cfd.custom_field_id
I tested this on 3 tables I have with a similar setup, so I think it should work; names are subject to change.
Update:
select ud.firstname, ud.lastname, group_concat(cf.name)
from user_data as ud
join custom_field_data as cfd
on cfd.user_id = ud.user_id
join custom_fields as cf
on cf.custom_field_id = cfd.custom_field_id
group by ud.user_id
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Let's start with a simple connection to your table custom_field_data
to user_data
, where the values and field names are hard-coded:
SELECT
u.*,
f1.value as "<Field 1 Name>",
...
f2.value as "<Field N Name>"
FROM
user_data u LEFT JOIN
custom_field_data f1 ON u.user_id = f1.user_id AND f1.custom_field_id = 1
LEFT JOIN
custom_field_data f ON u.user_id = fn.user_id AND fn.custom_field_id = <N>
Now, if you want to extract data without hardcoding, you will need to build your SQL dynamically based on the data in the table custom_fields
:
SELECT * FROM custom_fields;
If some custom fields are never used against users, you would like to limit the number of custom fields as follows:
SELECT * FROM custom_fields f
WHERE EXISTS
(SELECT * FROM custom_field_data
WHERE f.custom_field_id = custom_field_id)
Finally, to create the required SQL in PHP, you need the following lines:
// Begin SELECT clause (static):
$sql = "SELECT u.*,"
// Add all fields that you selected form the custom_fields:
foreach ($result as $row) { // Don't forget to handle commas
$sql = $sql + <expression that gets codes and name>
}
// Start FROM clause (static):
$sql = $sql + " FROM user_data u "
// Join to custom_field_data:
foreach ($result as $row) {
$sql = $sql + " LEFT JOIN custom_field_data <alias expression> ON ..
}
At the end, you should end up with a SQL string that attaches users to custom_field_data
for each available custom field.
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perhaps o pull the data with $.ajax()
and PHP
. Create a file data.php
, we are going to load this file with ajax
. In the file, data.php
write this code.
$query = mysqli_query("select * from custom_field_data
inner join
user_data on user_data.user_id = custom_field_data.user_id
inner join
custom_fields on custom_field_data.custom_field_id = custom_fields.custom_field_id");
<table>
<caption>table title and/or explanatory text</caption>
<thead>
<tr>
<th>User ID</th>
<th>First Name</th>
<th>Last Name</th>
<th>Field Name 1</th>
<th>Field Name 2</th>
<th>Field Name 3</th>
<th>Field Name 4</th>
<th>Field Name 5</th>
</tr>
</thead>
<tbody>
<?php
while ($row = mysqli_fetch_array($query)) {
echo "<tr>
<td>" .$row{'user_id'}. "</td>
<td>" .$row{'first_name'}. "</td>
<td>" .$row{'last_name'}. "</td>
<td>" .$row{'field_name_1'}. "</td>
<td>" .$row{'field_name_2'}. "</td>
<td>" .$row{'field_name_3'}. "</td>
<td>" .$row{'field_name_4'}. "</td>
<td>" .$row{'field_name_5'}. "</td>
</tr>";
}
?>
</tbody>
On the main page, use button
to load data.
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
<script type="text/javascript">
$(function(){
$('#load-data').click(function(){
$.post('data.php', function(data){
$('#results').html(data);
});
});
});
</script>
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The best way in my opinion is to use a connection because it will reduce the size of the data transferred between the DB and PHP
You can use JSON as it is lightweight.
You can keep things hidden in a hidden box and use them to further filter on the client side completely
update -
For Sql server, I would write a query like this
select
t1.user_name,
t1.first_name,
t1.last_name,
(select name from custom_fields
where custom_field_id= t2.custom_field_id)
from
user_data t1 left join
custom_field_data t2 on t1.user_id=t2.userid
Change this to match my-sql
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